Conventionally broadly known sulfonylimidic acid compounds and phosphorylimidic acid compounds are useful substances as pharmaceutical intermediates and agrochemical intermediates, as well as acid catalysts, ionic liquids, and antistatic agents. These compounds have been used in recent years for electrolytes of energy devices, such as Li batteries, fuel cells, and electric double layer capacitors.
Electrolytes of these energy devices are required to have characteristics such as a high ionic conductivity. As a means for improving the ionic conductivity, for example, as disclosed in Patent Document 1, Non-patent Document 1, and Non-patent Document 2, there have been efforts to improve an ionic conductivity by increasing the number of counter cations within one molecule through the use of diimide, dimethide or triimide as anion. However, a perfluoroalkyl group is essential for these divalent or higher valent anions in order to increase acidity. However, the introduction of a perfluoroalkyl group is inefficient, since this results in an increase in the molecular weight of the anion, and a decrease in the number of counter cations per molecular weight. Furthermore, the molecular weight is high, so that the viscosity tends to increase to lower the ionic conductivity, when it is dissolved in the electrolytic solution of an energy device. Furthermore, a perfluoroalkyl group is very expensive and this is a disadvantage for industrial mass production. Furthermore, the use of a diimidic acid compound having a perfluoroalkylsulfonyl group or an imidic acid compound having a sulfonate group (—SO3−) is difficult, since these compounds corrode aluminum that is an electrode collector when used for electrolytes of energy devices.